Mark assembly as CLS compliant

[flobernd]

Adds the CLSCompliant(true) attribute on assembly level.

This allows the SemVersion class to be used in other CLS compliant libraries as e.g. a public class member.

More information: https://learn.microsoft.com/en-us/dotnet/standard/language-independence

The library itself already is fully CLS compliant, just the attribute was missing.